phr
Bluelighter
First off, the guys using the numbering are talking about heroin base, which is #2. 
The OP either has #2 or has #4 with an insoluble cut. Since he's in the US, the latter is a much greater likely hood. Doesn't guarantee it though...
The best advice would be to just snort it if you don't have a micron filter. Adding heat isn't necessary, and it might end up dissolving more of the cut. Some say that heat will kill bacteria, but that's negligible since you're not applying it for long enough. Add in the likely hood of destroying your sought off product, and it makes sense to not add heat.

The OP either has #2 or has #4 with an insoluble cut. Since he's in the US, the latter is a much greater likely hood. Doesn't guarantee it though...
The best advice would be to just snort it if you don't have a micron filter. Adding heat isn't necessary, and it might end up dissolving more of the cut. Some say that heat will kill bacteria, but that's negligible since you're not applying it for long enough. Add in the likely hood of destroying your sought off product, and it makes sense to not add heat.